This invention relates to a process and an apparatus for detecting loop stitches of a tubular knitted fabric and an apparatus for linking the tubular knitted fabric, and more particularly to the process and apparatus, which accurately detect the location of each loop stitch formed, for instance, in the tubular knitted fabric, and the apparatus which can link the tubular knitted fabric, based on the thus detected stitches.
Conventionally, in a knitted fabric for use as a material in a knitted product, in order to correctly link stitches of the product so as to have required size and shape, loop stitches which each have a larger loop than those of other stitches are formed of knitting yarn with slightly looser or larger stitches. When the loop stitches are linked, the operator stretches and enlarges the knitted fabric by his hands, and peers into the knitted fabric to find loop stitches. Then, he sets the fabric by manually inserting a point needle of a linking apparatus into the loop stitches, followed by sewing the fabric by a sewing machine. This linking operation is the same as in linking a tubular knitted fabric. First, the operator puts his hands into an open portion of the tubular knitted fabric to stretch and enlarge the same, and peers into the knitted fabric on a backward side thereof with respect to the operator, to find the loop stitches. Then, he sets the fabric by inserting the point needle of the linking apparatus into the loop stitches, followed by performing the same operation to the fabric on a frontward side with respect to the operator. Further, he superposes the loop stitches to be linked on each other, and sets the loop stitches to the point needle, followed by sewing the fabric by the sewing machine, to thereby perform linking.
Although to find the entire loop stitches as a row is relatively easy, to correctly find each of loop stitches requires experience and skill of the operator, since the loop stitches are formed by knitting yarn only with slightly loose or large stitches compared with other stitches. Therefore, for a person not skilled in the operation, an operation to find the loop stitches by observation requires a very long time period, which results in extremely degraded working efficiency. Especially, in the linking of tubular knitted fabrics, once the knitted fabric on the backward side is set to the linking apparatus, it is difficult to stretch the knitted fabric on the frontward side, and hence the above-mentioned degraded working efficiency becomes worse. Therefore, when the linking is performed, an inconvenience such as omission of linking at several loop stitches is unfavorably generated, resulting in reduced yield of products.
Therefore, it is a first object of the invention to provide a process for detecting loop stitches of a tubular knitted fabric, which is capable of automatically detecting each of the loop stitches formed in the tubular knitted fabric.
It is a second object of the invention to provide an apparatus for detecting the loop stitches, according to the above process.
It is a third object of the invention to provide an apparatus for linking the tubular knitted fabric, according to the above process.
To attain the first object, the invention provides a process for detecting loop stitches of a tubular knitted fabric, comprising the steps of extending the tubular knitted fabric by penetrating a penetration element through an interior of the tubular knitted fabric having the loop stitches formed therein, picking up a multi-gradation image including an image of loop stitches of the tubular knitted fabric extended by the penetration element, and detecting locations of the loop stitches by processing the multi-gradation image.
According to the process of the invention, an image of the knitted fabric on a frontward surface and an image of the knitted fabric on a backward surface are independently picked up, while stitches inclusive of the loop stitches are enlarged. As a result, the images of the knitted fabric on the frontward surface and the backward surface are prevented from being confused with each other, whereby locations of the loop stitches can be accurately detected.
The process may include the step of extending the tubular knitted fabric in a penetration direction of the penetration element.
According to the process, the image of the stitches inclusive of the loop stitches can be picked up in a further enlarged state. As a result, the locations of the loop stitches can be more accurately detected.
Further, the step of picking up multi-gradation image may be carried out in one plane.
According to the process, the image of a portion in the vicinity of the loop stitches of the tubular knitted fabric is picked up on a two-dimensional basis. As a result, the image of a plurality of the loop stitches can be collectively and simultaneously picked up, which dispenses with separate image pickup of each of the loop stitches of the tubular knitted fabric, leading to shortening of a detecting time period and hence improvement in detection efficiency.
The step of picking up multi-gradation image may be carried out by using light transmitted from the interior of the tubular knitted fabric to the exterior of the same. A plurality of emitters, e.g. LED may be arranged on an end surface of the penetration element, defining the slit, to thereby irradiate the stitches arranged on the slit from the inside of the slit.
According to the process, light transmitted through the tubular knitted fabric is received by image pickup means. As a result, the multi-gradation image is picked up, in which boundaries between fiber areas and stitch areas of the tubular knitted fabric can be clearly discriminated, whereby the locations of the loop stitches can be more accurately detected.
Further, the penetration element may be composed of an element having a slit therein, and the step of picking up multi-gradation image may include the steps of irradiating the slit, and using light transmitted from one side of the exterior of the tubular knitted fabric to the other side of the same through the slit.
According to the process, light transmitted through the tubular knitted fabric arranged on the slit is also received by the image pickup means. As a result, the multi-gradation image is picked up, in which the boundaries between the fiber areas and the stitch areas of the tubular knitted fabric arranged on the slit can be clearly discriminated, whereby the locations of the loop stitches on the slit can be more accurately detected.
Still further, the step of detecting the locations of the loop stitches may comprise the steps of converting the multi-gradation image into a binary image, converting the binary image into a labeled image composed of labeled regions, counting the number of picture elements of each of the labeled regions in the labeled image, and then extracting only labeled regions each having a larger number of picture elements than a predetermined value, the predetermined value being set to a value larger than a reference value corresponding to a minimum value of the number of picture elements forming a labeled region of each of the loop stitches in the labeled image, to thereby generate an extracted labeled image, and determining a location of each of the loop stitches by calculating a location of the labeled region of each of the loop stitches in the extracted labeled image.
According to the process, the loop stitch is extracted based on an area of a loop stitch region, and then the location of the loop stitch is determined. As a result, the locations of the loop stitches with various sizes can be detected.
The step of converting the multi-gradation image into the binary image may include the step of dividing the multi-gradation image into a plurality of small regions, and determining a binarization threshold value for each of the small regions, based on image features of each of the small regions.
In the process, the image of each portion is binarized according to illumination of each portion of the tubular knitted fabric. As a result, the boundaries of the fiber areas and the stitch areas are detected irrespective of the influence of the illumination of each portion of the tubular knitted fabric, leading to further accurate detection of the loop stitches.
According to the second object, the invention provides an apparatus for detecting loop stitches of a tubular knitted fabric, comprising a penetration element for extending the tubular knitted fabric by penetrating the same through an interior of the tubular knitted fabric having the loop stitches formed therein, image pickup means for picking up a multi-gradation image including an image of loop stitches of the tubular knitted fabric extended by the penetration element, and loop stitch detecting means for detecting locations of the loop stitches by processing the multi-gradation image.
According to the apparatus of the invention, an image of the knitted fabric on a frontward surface and an image of the knitted fabric on a backward surface are independently picked up, while stitches inclusive of the loop stitches are enlarged. As a result, the images of the knitted fabric on the frontward surface and the backward surface are prevented from being confused with each other, whereby the locations of the loop stitches can be accurately detected.
The apparatus may include upper retaining means for retaining the tubular knitted fabric at a location upper than the loop stitches, to thereby move the tubular knitted fabric in a penetration direction of the penetration element, and lower retaining means for retaining the tubular knitted fabric at a location lower than the loop stitches, to thereby move the tubular knitted fabric in the penetration direction of the penetration element.
According to the apparatus, the image of the stitches inclusive of the loop stitches can be picked up in a further enlarged state. As a result, the locations of the loop stitches can be more accurately detected.
Further, the penetration element may have surfaces on which the loop stitches are arranged, at least the surfaces of the penetration element being made flat, and the image pickup means may be disposed such that image pickup directions thereof are set at right angles with respect to a lateral direction of the flat surfaces of the penetration element.
According to the apparatus, the image of a portion in the vicinity of the loop stitches of the tubular knitted fabric is picked up on a two-dimensional basis. As a result, the image of a plurality of the loop stitches can be collectively and simultaneously picked up. Especially, when the loop stitches are arrange in a state where each of the location thereof is not necessary to be adjusted, separate image pickup of each of the loop stitches can be dispensed with, leading to shortening of a detecting time period and hence improvement in detection efficiency.
The penetration element may include light emitting means.
According to the apparatus, light transmitted through the tubular knitted fabric is received by the image pickup means. As a result, the multi-gradation image is picked up, in which boundaries between fiber areas and stitch areas of the tubular knitted fabric can be clearly discriminated, whereby the locations of the loop stitches can be more accurately detected.
Further, the penetration element may have a slit formed therein, and irradiating means for irradiating the slit.
According to the apparatus, light transmitted through the tubular knitted fabric arranged on the slit is also received by the image pickup means. As a result, the multi-gradation image is picked up, in which the boundaries between the fiber areas and the stitch areas of the tubular knitted fabric arranged on the slit can be clearly discriminated, whereby the locations of the loop stitches on the slit can be more accurately detected. The apparatus may have a device such as one composed of a plurality of emitters, e.g. LED arranged on an end surface of the penetration element, defining the slit, to thereby irradiate the stitches arranged on the slit from the inside of the slit.
Still further, the loop stitch detecting means may comprise means for converting the multi-gradation image into a binary image, means for converting the binary image into a labeled image composed of labeled regions, region extracting means for counting the number of picture elements of each of the labeled regions in the labeled image, and then extracting only labeled regions each having a larger number of picture elements than a predetermined value, the predetermined value being set to a value larger than a reference value corresponding to a minimum value of the number of picture elements forming a labeled region of each of the loop stitches in the labeled image, to thereby generate an extracted labeled image, and means for determining a location of each of the loop stitches by calculating a location of the labeled region of each of the loop stitches in the extracted labeled image.
According to the apparatus, the loop stitch is extracted based on an area of a loop stitch region, and then the location of the loop stitch is determined. As a result, the loop stitches and stitches other than those can be discriminated, to thereby correctly determine the location of each loop stitch.
The means for converting the multi-gradation image into the binary image may include means for dividing the multi-gradation image into a plurality of small regions, and determining a binarization threshold value for each of the small regions, based on image features of each of the small regions.
In the apparatus, the image of each portion is binarized according to illumination of each portion of the tubular knitted fabric. As a result, the boundaries of the fiber areas and the loop stitch areas are detected irrespective of the influence of the illumination of each portion of the tubular knitted fabric, leading to further accurate detection of the loop stitches.
To attain the third object, the invention provides an apparatus for linking a tubular knitted fabric having loop stitches formed therein, comprising a penetration element for extending the tubular knitted fabric by penetrating the same through an interior of the tubular knitted fabric having the loop stitches formed therein, image pickup means for picking up a multi-gradation image including an image of loop stitches of the tubular knitted fabric extended by the penetration element, loop stitch detecting means for detecting locations of the loop stitches by processing the multi-gradation image, a point needle for being inserted into the loop stitches, means for guiding the point needle to the locations of the loop stitches detected by the loop stitch detecting means, means for inserting the point needle to each of the loop stitches, and a sewing machine mechanism for linking the loop stitches into which the pointing needle is inserted.
According to the apparatus of the invention, an image of the knitted fabric on a frontward surface and an image of the knitted fabric on a backward surface are independently picked up, while stitches inclusive of the loop stitches are enlarged. As a result, the images of the knitted fabric on the frontward surface and the backward surface can be prevented from being confused with each other, and therefore the point needle can be accurately inserted into the loop stitches, to thereby correctly link the fabric so as to have desired size and shape.
The apparatus may include upper retaining means for retaining the tubular knitted fabric at a location upper than the loop stitches, to thereby move the tubular knitted fabric in a penetration direction of the penetration element, and lower retaining means for retaining the tubular knitted fabric at a location lower than the loop stitches, to thereby move the tubular knitted fabric in the penetration direction of the penetration element.
According to the apparatus, the image of the stitches inclusive of the loop stitches is picked up in a more enlarged state. As a result, the locations of the loop stitches can be more accurately detected, and the fabric can be correctly linked with the desired size and shape without fail.
Further, the penetration element may have surfaces on which the loop stitches are arranged, at least the surfaces of the penetration element being made flat, and the image pickup means may be disposed such that image pickup directions thereof are set at right angles with respect to the flat surfaces of the penetration element.
According to the apparatus, the image of a portion in the vicinity of the loop stitches of the tubular knitted fabric is picked up on a two-dimensional basis. As a result, the image of a plurality of the loop stitches can be collectively and simultaneously picked up, which dispenses with separate image pickup of each of the loop stitches, leading to shortening of a linking time period and hence improvement in production efficiency.
The penetration element may include light emitting means.
According to the apparatus, light transmitted through the tubular knitted fabric is received by the image pickup means. As a result, the multi-gradation image is picked up, in which boundaries between fiber areas and stitch areas of the tubular knitted fabric can be clearly discriminated, whereby the locations of the loop stitches can be more accurately detected.
Further, the penetration element may have a slit formed therein, and irradiating means for irradiating the slit.
According to the apparatus, light transmitted through the tubular knitted fabric arranged on the slit is also received by the image pickup means. As a result, the multi-gradation image is picked up, in which the boundaries between the fiber areas and the stitch areas of the tubular knitted fabric arranged on the slit can be clearly discriminated, whereby the locations of the loop stitches on the slit can be more accurately detected. Further, the same point needle can be inserted into the loop stitches on the frontward surface and backward surface of the knitted fabric, to thereby link the fabric.
Still further, the loop stitch detecting means comprise means for converting the multi-gradation image into a binary image, means for converting the binary image into a labeled image composed of labeled regions, region extracting means for counting the number of picture elements of each of the labeled regions present in the labeled image, and then extracting only labeled regions each having a larger number of picture elements than a predetermined value, the predetermined value being set to a value larger than a reference value corresponding to a minimum value of the number of picture elements forming a labeled region of each of the loop stitches in the labeled image, to thereby generate an extracted labeled image, and means for determining a location of each of the loop stitches by calculating a location of the labeled region of each of the loop stitches in the extracted labeled image.
According to the apparatus, the loop stitch is extracted based on an area of a loop stitch region, and then the location of the loop stitch is determined. As a result, the loop stitches and the stitches other than those can be discriminated, to thereby correctly determine the location of each loop stitch.
The means for converting the multi-gradation image into the binary image may include means for dividing the multi-gradation image into a plurality of small regions, and determining a binarization threshold value for each of the small regions, based on image features of each of the small regions.
In the apparatus, the image of each portion is binarized according to illumination of each portion of the tubular knitted fabric. As a result, the boundaries between the fiber areas and the stitch areas are detected irrespective of the influence of the illumination of each portion of the tubular knitted fabric, leading to further accurate detection of the loop stitches, whereby the locations of the loop stitches can be more accurately detected.
The means for guiding the point needle to the locations of the loop stitches may include means for moving the locations of the loop stitches in one direction, and means for moving the point needle in one direction orthogonal to the former direction. Further, the means for guiding the point needle to the locations of the loop stitches may include means for moving the point needle on a two-dimensional basis. Still further, the means for guiding the point needle to the locations of the loop stitches may include means for moving the locations of the loop stitches on a two-dimensional basis.
According to the apparatus, by moving the locations of the loop stitches and the location of the point needle, the point needle can be correctly guided to the locations of the loop stitches.
The above and other objects, features and advantages of the invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.